The present invention relates in one of its aspects to a blind fastener, and in another of its aspects to a method of installation of such a blind fastener into a suitable workpiece.
The term “fastener” is used to include, for example, a rivet which secures together two or more members forming a workpiece, and also, for example, a threaded insert which, when installed in a workpiece, allows a screw to be engaged therewith to secure another member to the workpiece. Such a threaded insert may be such that it will also secure together two or more members forming a workpiece.
By “blind” is meant a fastener which can be installed in the workpiece by access to only the front or near side of the workpiece.
It is clearly advantageous if the number of separate operations involved in such installation can be reduced. Most such fasteners require the provision of a suitable pre-formed hole through the workpiece through which the fastener is inserted. Fasteners which drill their own hole do exist, the fastener having teeth on its leading end to provide drilling means which with suitable rotation of, and axial pressure on, the fastener drills a suitable hole. However, such an arrangement has numerous practical disadvantages. These may be summarized as follows:
1. additional cost of manufacture and inspection of drill teeth on each fastener, and of non-damaging handling thereof after manufacture;
2. skidding or skating of the core drill across the workpiece face when attempting initial location;
3. mechanical damage to the workpiece, especially if the latter is laminated i.e. consists of more than one member;
4. the insert must be circular in exterior section along all of that part of its length which enters the hole;
5. the drilling operation produces debris from the workpiece, and a drilled-out slug, which may be inconvenient and possibly dangerous;
6. the drill teeth on the installed fastener can provide a hazard on the blind side of the workpiece.
The present invention aims to provide a fastener, and a method of installation of such a fastener, which overcomes these disadvantages.